INTRODUCTION
1 Australian Historical Population Statistics is a compendium electronic release which contains a wide range of historical demographic data on a variety of topics. The data are presented in spreadsheet format (Microsoft Excel) going back, where possible, to the beginnings of European settlement (1788) of Australia.
2 This product is updated periodically. More up-to-date information may be available from the source products stated at the bottom of each spreadsheet. A list of related Australian Bureau of Statistics (ABS) and other publications can also be found below.

UPDATES
3 Tables based on Marriage, Divorces and Marital Status have been discontinued as data on registered marriage does not give a complete picture of the formation of partnerships and and families today, due to the increasing incidence of social (or de facto) marriages. Please see explanatory note 69 for further information on Marriage, Divorces and Marital Status. The previous release of this this product provides data on marriages, divorces and marital status up until 2006.4 The following is a record of updates made to the historical series:

Australian Demography Bulletins produced by the Commonwealth Bureau of Census and Statistics;

Commonwealth censuses;

ABS demography publications; and

other ABS demography collections.

7 A summary of 19th century statistics collected by the colonial statistical bureaux can be found in the ABS publication Catalogue of Australian Statistical Publications, 1804 to 1901 (cat. no. 1115.0).
8 Early estimates of the Australian Aboriginal and Torres Strait Islander population have been compiled from The Aboriginal Population of Australia (1980) by L.R. Smith, please refer to explanatory note 76 for the full reference. More recent estimates have been compiled from the Census of Population and Housing and other ABS demography collections.
9 Given that different sources often exist for the same data, minor discrepancies may exist between Australian Historical Population Statistics and these sources. References to the source(s) of information used to compile these statistics are given at the bottom of each spreadsheet.

COLONIES, STATES AND TERRITORIES
10 The terms 'state' and 'territory' are used to describe states and territories as they exist in the post-Federation period, as well as the various colonies that existed prior to Federation. For example, data presented in the tables under the heading 'NSW' relates to both the colony of New South Wales and the state of New South Wales.
11 Tasmania, Victoria and Queensland became independent from New South Wales in the years 1825, 1851 and 1859 respectively. Western Australia and South Australia came into existence in 1829 and 1836 respectively.
12 The Northern Territory and the Australian Capital Territory (ACT) came under the control of the Federal Government in 1911 and were no longer included in the estimates for South Australia and New South Wales respectively. Although the Northern Territory ceased to exist briefly between 1 February 1927 and 11 June 1931, being replaced by the territories of North Australia and Central Australia, for purposes of comparison the figures for combined North Australia and Central Australia are described as "Northern Territory" in Table 3.2 for the periods 1927-1931.
13 Following the 1992 amendments to the Acts Interpretation Act to include the Indian Ocean Territories of Christmas Island and the Cocos (Keeling) Islands as part of geographic Australia, population estimates commencing from September quarter 1993 include estimates for these two territories. To reflect this change, another category at the state and territory level has been created, known as Other Territories. Other Territories include Jervis Bay Territory (included in ACT estimates from 1915 to June quarter 1993), as well as Christmas Island and the Cocos (Keeling) Islands which were previously excluded from population estimates for Australia.

POPULATION ESTIMATES
14 In this publication, the term population refers to the counts of people in Australia, regardless of the method of enumeration from 1788 to the present day. Australian Historical Population Statistics uses four measures of population: actual location census counts, usual residence census counts, population estimates and the estimated resident population (ERP).
15 Actual location census counts are counts of all people, within the scope of the census, who spent census night in Australia. People are counted where they were at the time of the census, which may not be where they usually live. In contrast, usual residence census counts are counts of all people, based on where they usually live, rather than where they were on census night. Overseas visitors are excluded from usual residence data.
16 Early population estimates were obtained through colonial musters and, from 1828, through a series of relatively regular colonial censuses. The dates of these colonial censuses are shown in Table 1 below. In 1910, on the basis of the early musters and other colonial records, an annual series of population totals for the states was published for all years commencing from December 1788, the year of the first European settlement in Australia. They are disaggregated by sex from 1796.
17 The first simultaneous censuses of all Australian colonies was taken in 1881 and the first national census was taken in 1911. It was followed by others in 1921, 1933, 1947, 1954 and 1961. Since 1961 censuses have been conducted at five yearly intervals.

Table 1. Australian censuses, 1828 to 2011

Year

NSW

Vic.

Qld

SA

WA

Tas.

NT

ACT

Australia

1828

Nov.

. .

. .

. .

. .

. .

. .

. .

. .

1833

2 Sep.

. .

. .

. .

. .

. .

. .

. .

. .

1836

2 Sep.

. .

. .

. .

. .

. .

. .

. .

. .

1841

2 Mar.

. .

. .

. .

. .

27 Sep.

. .

. .

. .

1844

. .

. .

. .

26 Feb.

. .

. .

. .

. .

. .

1846

2 Mar.

. .

. .

26 Feb.

. .

. .

. .

. .

. .

1847

. .

. .

. .

. .

. .

31 Dec.

. .

. .

. .

1848

. .

. .

. .

. .

10 Oct.

. .

. .

. .

. .

1851

1 Mar.

. .

. .

1 Jan.

. .

1 Mar.

. .

. .

. .

1854

. .

(a)26 Apr.

. .

. .

30 Sep.

. .

. .

. .

. .

1855

. .

. .

. .

31 Mar.

. .

. .

. .

. .

. .

1856

1 Mar.

. .

. .

. .

. .

. .

. .

. .

. .

1857

. .

29 Mar.

. .

. .

. .

31 Mar.

. .

. .

. .

1859

. .

. .

. .

. .

31 Dec.

. .

. .

. .

. .

1861

7 Apr.

7 Apr.

(a)7 Apr.

7 Apr.

. .

7 Apr.

. .

. .

. .

1864

. .

. .

1 Jan.

. .

. .

. .

. .

. .

. .

1866

. .

. .

. .

26 Mar.

. .

. .

. .

. .

. .

1868

. .

. .

2 Mar.

. .

. .

. .

. .

. .

. .

1870

. .

. .

. .

. .

31 Mar.

7 Feb.

. .

. .

. .

1871

2 Apr.

2 Apr.

1 Sep.

2 Apr.

. .

. .

. .

. .

. .

1876

. .

. .

1 May

26 Mar.

. .

. .

. .

. .

. .

1881(b)

3 Apr.

3 Apr.

3 Apr.

3 Apr.

3 Apr.

3 Apr.

(c)3 Apr.

. .

3 Apr.

1886

. .

. .

1 May

. .

. .

. .

. .

. .

. .

1891

5 Apr.

5 Apr.

5 Apr.

5 Apr.

5 Apr.

5 Apr.

5 Apr.

. .

5 Apr.

1901

31 Mar.

31 Mar.

31 Mar.

31 Mar.

31 Mar.

31 Mar.

31 Mar.

. .

31 Mar.

1911

3 Apr.

3 Apr.

3 Apr.

3 Apr.

3 Apr.

3 Apr.

3 Apr.

(a)3 Apr.

3 Apr.

1921

4 Apr.

4 Apr.

4 Apr.

4 Apr.

4 Apr.

4 Apr.

4 Apr.

4 Apr.

4 Apr.

1933

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

1947

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

1954

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

1961

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

1966

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

1971

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

1976

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

1981

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

1986

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

30 Jun.

1991

6 Aug.

6 Aug.

6 Aug.

6 Aug.

6 Aug.

6 Aug.

6 Aug.

6 Aug.

6 Aug.

1996

6 Aug.

6 Aug.

6 Aug.

6 Aug.

6 Aug.

6 Aug.

6 Aug.

6 Aug.

6 Aug.

2001

7 Aug.

7 Aug.

7 Aug.

7 Aug.

7 Aug.

7 Aug.

7 Aug.

7 Aug.

7 Aug.

2006

8 Aug.

8 Aug.

8 Aug.

8 Aug.

8 Aug.

8 Aug.

8 Aug.

8 Aug.

8 Aug.

2011

9 Aug.

9 Aug.

9 Aug.

9 Aug.

9 Aug.

9 Aug.

9 Aug.

9 Aug.

9 Aug.

. . not applicable

(a) Previously included with NSW.

(b) The first simultaneous census of all Australian colonies.

(c) Included with SA for the censuses of 1866, 1871 and 1876. The NT was transferred to the Commonwealth on 1 January 1911.

18 Population estimates from Federation (1901) to 1971 are based on unadjusted (for under enumeration) census counts on an actual location basis, updated for post-censal years according to registered births and deaths by state/territory of registration, and interstate and overseas migration. From 1971 onwards, the concept of estimated resident population (ERP) is used, which links people to their place of usual residence. ERP was introduced following the 1981 census and backdated to 1971.

Estimated Resident Population

19 Estimated resident population (ERP) is an estimate of the Australian population obtained by adding to the estimated population at the beginning of each period the components of natural increase (on a usual residence basis) and net overseas migration. For the states and territories, account is also taken of estimated interstate movements involving a change of usual residence. ERP is derived from usual residence census counts, to which are added the estimated net census undercount and Australian residents estimated to have been temporarily overseas at the time of the census. Overseas visitors in Australia and Australians resident overseas are excluded from the ERP.

20 After each census, estimates for the preceding intercensal period are revised by incorporating an additional adjustment (intercensal discrepancy) to ensure that the total intercensal increase agrees with the difference between the ERPs at the two 30 June dates in the respective census years.

21 Following the 2011 Census, a decision was made to recast historical ERP data back to 1991 in response to the unusually high ‘intercensal error’ (i.e. the difference between unrebased estimates and the preliminary Census-based estimate), resulting from a change in the methodology used to estimate undercount in the 2011 Census. This decision is documented in three issues of Australian Demographic Statistics (cat. no. 3101.0) released on 20 June 2012, 27 September 2012 and 18 December 2012. When comparing the original ERP series with the recast series, the proportionality of age groups, states and territories and sexes are not significantly changed. In addition, while previous ERP levels have been lowered, growth rates remain relatively consistent with those published before rebasing to the 2011 Census. Fertility, mortality, and other measures which use ERP as a denominator in this publication have also been revised back to 1991 (unless otherwise indicated). For further information see Final Rebasing of Australia's Population Estimates, September Quarter 2006 – June Quarter 2011 and Recasting 20 Years of ERP.

22 ERP data to June 2011 is featured in the Population size and growth, Population distribution and Population age-sex structure data cubes, and is used to calculate the various rates found in the Births, Deaths, Life tables and Migration data cubes.

24 From July 1976, final intercensal difference (previously known as intercensal discrepancy) is recorded as a separate component of population change. For the period July 1971 to June 1976 no intercensal discrepancy exists due to the method used to produce resident population estimates. Prior to July 1971, intercensal discrepancies were incorporated into the overseas and interstate migration components of population change. See Glossary for more information.

25 For further information on each population component please see the Births, Deaths, Net Overseas Migration and Interstate Migration sections of these explanatory notes.

ABORIGINAL AND TORRES STRAIT ISLANDER POPULATION
26 Estimates of the Aboriginal and Torres Strait Islander population were first produced by the ABS in 1994 for the years 1986 to 1991 (cat. no. 3230.0). Estimates for 1991 to 1996 based on the 1996 Census were published in 1998 (cat. no. 3230.0). Estimates for 1991 to 2001 based on 2001 Census were published in Experimental Estimates and Projections, Aboriginal and Torres Strait Islander Australians, 1991 to 2009 (cat. no. 3238.0). Aboriginal and Torres Strait Islander estimates and projections based on the 2011 Census data were released in Estimates and Projections, Aboriginal and Torres Strait Islander Australians, 2001 to 2026 (cat. no. 3238.0). A time series based on the 2016 Census is expected to be released in 2019.
27 Since 1981, all ABS Aboriginal and Torres Strait Islander population statistics are based on responses to the ABS standard question for Aboriginal and Torres Strait Islander identification, which is used in self-enumerated collections. The same census question has been used to determine Aboriginal and Torres Strait Islander status (but not its component peoples) since the 1981 Census. There are no accurate estimates of the population of Australia before European settlement. Many estimates were based on post-1788 observations of a population already reduced by introduced diseases and other factors. Smith (1980) estimated the absolute minimum pre-1788 population at 315,000, please refer to explanatory note 76 for the full reference. Other estimates put the figure at over one million people, while recent archaeological evidence suggests that a population of 750,000 could have been sustained.
28 Until 1967, section 127 of the Constitution required the exclusion of 'Aboriginal natives' from estimates of the population of Australia. 'Aboriginal natives' were interpreted as being people who had more than 50% Aboriginal 'blood'. This provision was repealed with the proclamation of the Constitution Alteration (Aboriginals) Act 1967 so that since 10 August 1967 population statistics were to officially include 'full-blooded' Aboriginal and Torres Strait Islander people.
29 From the 1971 Census onwards, Aboriginal and Torres Strait Islander persons have no longer been asked to state their degree of Aboriginal and Torres Strait Islander descent. Since this time, In 1996, for example, the census question has asked 'Is the person of Aboriginal or Torres Strait Islander origin?'. Changing social attitudes, political developments, improvements in census coverage and a broader definition of 'Aboriginal' and 'Torres Strait Islander' are likely to have contributed to the rapidly rising numbers of Aboriginal and Torres Strait Islander people that have been recorded since 1971.
30 The latest available Aboriginal and Torres Strait Islander population estimates are 2011 Census based.
31 For further information refer to the Census of Population and Housing: Understanding the Increase in Aboriginal and Torres Strait Islander Counts, 2006-2011 (cat. no. 2077.0).

POPULATION DISTRIBUTION
32 Population estimates for each reference date are presented based on a consistent statistical geography, however caution must be exercised when comparing populations across time as they may be based on different boundaries. Refer to the footnotes for each table for more information about statistical geography used in that table. For further information refer to the ABS Geography Australian Statistical Geography Standard home page.
33 The regions specified in this publication are Greater Capital City Statistical Areas (GCCSAs), Significant Urban Areas (SUAs), Local Government Areas (LGAs), and urban and rural areas. GCCSAs represent the socioeconomic area of each of the eight state and territory capital cities. SUAs represent concentrations of urban development with populations of 10,000 people or more. LGAs are legally designated areas over which incorporated local governments have responsibility.

34 Urban and Rural areas are as defined for the Census conducted on or near the reference date. In the 2011 Census, Urban and Rural areas were based on the ABS Section of State structure, which aggregates Urban Centres and Localities on the basis of population ranges. In 2011, urban areas represent combinations of Urban Centres, Rural areas represent the remaining parts of the country including Bounded Localities. Urban and Rural areas were defined under similar definitions in previous Censuses.
35 Regional population estimates based on the concept of usual residence have been produced since the 1970s. [Usual residence within Australia refers to that address at which the person has lived or intends to live for a total of six months or more in a given reference year]. Prior to this, population figures were calculated on an actual location concept [- that is, based on the number of persons actually present at that location at a given time]. Estimates based on actual location are generally higher in areas which attract short-term migrants, such as tourist areas, and this break in time series should be notedwhen comparing historical population estimates. For further information on regional population estimates see Regional Population Growth, Australia (cat. no. 3218.0).

POPULATION AGE-SEX STRUCTURE

36 Annual estimates of the population by single year of age and sex for Australia as a whole commenced in 1921 and for the individual states and territories in 1962. Prior to these years, estimates of the population by age and sex were only available for census years.

38 Registration of births is the responsibility of state and territory Registrars of Births, Deaths and Marriages. Births information is based on data provided on an information form completed by the parent(s) of the child. This form is the basis of data provided to the ABS by individual Registrars for compilation into aggregate statistics. For further information see Births, Australia (cat. no. 3301.0).
39 Unless otherwise indicated, birth statistics refer to live births registered during the calendar year shown. There is usually an interval between the occurrence and registration of a birth, and as a result, some births occurring in one year are not registered until the following year, or even later. This can be caused by either a delay by the parent(s) in submitting a completed form to the registry, or a delay by the registry in processing the birth.
40 Birth statistics prior to 1969 are presented on the basis of state or territory of registration. From 1969 onwards they are presented on the basis of the state or territory of usual residence of the mother, regardless of where in Australia the birth occurred or was registered. Births which take place outside Australia are excluded from the statistics.
41 Births to mothers who are usual residents of Australia's Other Territories are registered in other Australian states. Prior to 1993, births to mothers usually resident in Christmas Island and Cocos (Keeling) Islands were included with Offshore Areas and Migratory in Western Australia, while births to mothers usually resident in Jervis Bay Territory were included with the ACT.

DEATHS
42 Registration of deaths is the responsibility of the state and territory Registrars of Births, Deaths and Marriages. Information about the deceased is based on details supplied by a relative or other person acquainted with the deceased, an official of the institution where the death occurred, and on information supplied by a medical practitioner or a coroner as to the cause of death. This information is supplied to the ABS by the state and territory registrars for coding and compilation into aggregate statistics. For further information see Deaths, Australia (cat. no. 3302.0).

43 Unless otherwise indicated, death statistics refer to deaths registered during the calendar year shown. There is usually an interval between the occurrence and registration of a death, and as result, some deaths occurring in one year are not registered until the following year or even later.
44 Death statistics prior to 1971 are presented on the basis of state or territory of registration. From 1971 onwards they are presented on the basis of the state or territory of usual residence of the deceased, regardless of where in Australia the death occurred or was registered.
45 Deaths of overseas visitors in Australia are included in the statistics, and are classified according to the state or territory in which the death was registered. Deaths of Australian residents which took place outside Australia are not included in the statistics.

War time
46 As deaths of Australian residents which took place overseas are not included in the statistics, deaths of Australian troops overseas in World War I are excluded. Similarly, Australian troops who died overseas during World War II are not included in death statistics, however they have been removed from the population estimates.

LIFE TABLES
47 A life table is a statistical model used to represent the mortality of a population. In its simplest form, a life table is generated from age-specific death rates and the resulting values are used to measure mortality, survivorship and life expectancy.
48 Life tables are presented separately for males and females. The life table depicts the mortality experience of a hypothetical group of newborn babies throughout their entire lifetime. It is based on the assumption that this group is subject to the age-specific mortality rates of the reference period. Typically this hypothetical group is 100,000 in size.
49 Since 1995, life tables produced by the ABS differ from those published prior to 1995 in a number of important respects. Firstly, they are based on three years of deaths and population data. This is intended to reduce the impact of year-to-year statistical variations, particularly at younger ages where there are small numbers of deaths, and at very older ages where the population at risk is small. Secondly, the deaths and population data are based on Australian residents who are physically present in Australia over the three-year period i.e.Australian residents temporarily overseas are excluded as are deaths in Australia of overseas visitors. Thirdly, they have been actuarially graduated on the same principles which are used for the quinquennial Australian life tables prepared by the Australian Government Actuary. Fourthly, from 2012 a small refinement has also been made to the method to bring Australia's mortality rates (qx values) into line with other comparable countries. For further information see Life Tables, Australia (cat. no. 3302.0.55.001).

MIGRATION
Net overseas migration

50 According to recommendations of the United Nations, an international migrant is defined as "any person who changes his or her country of usual residence" (United Nations 1998). For the purposes of estimating net overseas migration (NOM), and thereby Australia's official ERP counts, a person is regarded as a usual resident if they have been (or expected to be) residing in Australia for a period of 12 months or more over a 16-month period. As such, NOM and ERP estimates include all people, regardless of nationality, citizenship or legal status, who usually live in Australia, with the exception of foreign diplomatic personnel and their families.
51 Conceptually, the term NOM is based on an international traveller's duration of stay being in or out of Australia for 12 months or more. It is the difference between the number of incoming travellers who stay in Australia for 12 months or more and are added to the population (NOM arrivals) and the number of outgoing travellers who leave Australia for 12 months or more and are subtracted from the population (NOM departures).Prior to 1 July 2006, NOM estimation methods used a 12/12 rule to determine if a traveller contributed to ERP. This meant that in order for a person to contribute to NOM they must stay in or be absent from Australia for a continuous period of 12 out of 12 months. From September quarter 2006, the new method for calculating NOM is used.
52 The current NOM estimation methods employ a '12/16 month rule' where the traveller can be added or subtracted from NOM if they have stayed in or been absent from Australia for a period of 12 months or more over a 16 month period. This period of 12 months does not have to be continuous. Although a traveller states their intended duration of stay on a passenger card, for NOM purposes the ABS now measures an individual's actual travel behaviour.
53 For further information on the improvements to NOM estimation and changes to the revision schedule for NOM, see the Information Paper: Improving Net Overseas Migration Estimation, Mar 2010 (cat. no. 3412.0.55.001). For further information on the '12/16 month rule' methodology see the Technical Note: '12/16 month rule' Methodology for Calculating Net Overseas Migration from September quarter 2006 onwards in Migration, Australia 2008-09 (cat. no. 3412.0). For more detailed information, see:

54 From July 1976 to June 2006 NOM was calculated as permanent and long-term arrivals less permanent and long-term departures, plus an adjustment for the effect of category jumping. This adjustment was necessary because net permanent and long-term migration figures were affected by changes in travel intentions from short-term to permanent/long-term or vice versa. Prior to July 1976 NOM was calculated by subtracting the number of total departures (permanent, long-term and short-term) out of Australia from the number of total arrivals (permanent, long-term and short-term) into Australia.

Category jumping and migration adjustment

55 Category jumping was a measure of the discrepancy between movements recorded as short-term, long-term or permanent at the time of movement, and the category recorded at the completion of a journey. Twelve months after a reference period it was determined whether the number of initially-recorded short-term, long-term and permanent arrivals and departures matched actual patterns of movement. This measure was used until the introduction of the 12/16 month methodology in July 2006.

57 Due to changes in the methods used to adjust NOM estimates, caution should be used comparing estimates over time. The table below describes the adjustment methods that have been applied to NOM estimates from September quarter 1976 and onwards.

War time
58 During World War I, troops leaving Australia were regarded as emigrants, while those returning were regarded as immigrants. This largely explains the record loss in 1916, and a large migration gain in 1919.
59 During World War II, troop movements between September 1939 and June 1947 were excluded from calculations of overseas migration.

Net interstate migration

60 Interstate migration is a key determinant of the accuracy of state and territory population estimates. Data on interstate migration cannot be directly estimated. Instead, post-censal estimates of interstate migration are modelled using administrative by-product data. Currently, the data used by the ABS are information on interstate changes of address advised to Medicare Australia and to the Department of Defence in the case of the military. The Medicare-based model used for generating post-censal estimates of interstate migration is then largely superseded when new Census information becomes available.

61 From 1986, data on interstate migration have been derived from information on interstate change of address advised by Medicare benefit recipients to Medicare Australia and to the Department of Defence in the case of the military. The ABS adjusts Medicare Australia data to make allowance for the number of persons who do not inform Medicare of their change of residence. Further details are available in Demography Working Paper 2004/1 - Review of Interstate Migration Method(cat. no. 3106.0.55.001) and Demographic Estimates and Projections: Concepts, Sources and Methods (cat. no. 3228.0).
62 When new Census data on interstate movements become available, part of the process of rebasing ERPs for states and territories is the re-derivation of interstate migration for the intercensal period. The overall approach is to minimise state preliminary intercensal difference using data analysed from the Census questions concerning an individual's place of residence one year ago, five years ago and on Census night. When new Census data are available, interstate migration estimates for the intercensal period are replaced with estimates derived from Census data on place of usual residence five years ago if these reduce preliminary intercensal difference. These estimates are then scaled to sum to zero at the Australian level. A similar process is carried out for the year prior to the Census, using Census data on place of usual residence one year ago. The difference between the original interstate migration estimates and the rebased estimates is apportioned across all quarters, movement categories, ages and sex categories in the intercensal period in order to minimise quarterly change. For more detailed information on the changes to the model see Information Paper: Review of Interstate Migration Method, March 2014 (cat. no. 3412.0.55.003).

63 Due to the fact that the Medicare data source is an indirect measure of interstate migration, the post-censal quarterly estimates of interstate migration have long been considered the weakest measure of the components of population change at the state and territory level. For further information on the process of estimating interstate migration and the administrative data used, see:

Defence force adjustment
64 Medicare theoretically covers all Australian usual residents as well as those non-Australian residents granted temporary Medicare registration. However, there are a range of Australian usual residents who do not access the Medicare system, primarily due to access to alternative health services. One group is the military. As such, estimates of interstate migration produced from the interstate migration model described in the Information Paper: Review of Interstate Migration Method, March 2014 (cat. no. 3412.0.55.003) are adjusted to compensate for defence force movements not covered by Medicare. These adjustments are estimated using counts of defence force personnel by age, sex and state/territory, obtained from the Department of Defence, with 70% of any change in quarterly defence numbers assumed to be due to interstate migration not otherwise covered by the model.

COUNTRY OF BIRTH
65 Country of birth classifications used by the ABS and preceding statistical agencies have changed over time. Tables presented in Australian Historical Population Statistics display the country of birth classifications in existence at the time of production of the data. For more detailed information on the most recent classification of countries, refer to the ABS publication Standard Australian Classification of Countries (SACC), 2011 (cat. no. 1269.0).

OVERSEAS ARRIVALS AND DEPARTURES
66 Statistics on overseas arrivals and departures (OAD) relate to the number of movements of travellers rather than the number of travellers. Care should be taken when using permanent and long-term movements data as it is known that some individuals who travel multiple times in a year are counted each time they cross Australia's borders. Permanent and long-term movements in this release are not an appropriate source of migration statistics. For further information refer to Australian Demographic Statistics (cat. no. 3101.0); the Information Paper: Statistical Implications of Improved Methods for Estimating Net Overseas Migration, Australia, 2007(cat. no. 3107.0.55.005); and the Technical Note: '12/16 month rule' Methodology for Calculating Net Overseas Migration from September quarter 2006 onwards in Migration, Australia (cat. no. 3412.0) under the Explanatory Notes tab.
67 OAD statistics are derived from a combination of full enumeration and sampling. All permanent movements and all movements with a duration of stay of one year or more are fully enumerated. The number of movements where the duration of stay is less than one year are fully enumerated, however their characteristics are sampled. From January 2005, about 5% of all short-term movements have been selected for sample. Statistics relating to these movements are therefore estimates which may differ from statistics which would have been obtained if details of all these movements had been processed. Sample standard errors can be found under Standard Errors in the Explanatory Notes tab of Overseas Arrivals and Departures, Australia (cat. no. 3401.0).
68 Prior to 1959, overseas arrivals and departures were classified as either permanent or temporary. Revised questions for travellers were introduced from 1 January 1959 which enabled arrivals and departures previously classified as permanent to be subdivided (as from 1 January 1959) into two categories: permanent movement and long-term movement.

69 For more information on Marriages, Births and Marital Status please see:

Data on marriages and divorces are no longer included in this publication. See Explanatory Note 3 for further information.

ACCURACY OF DATA
70 In commentary based on statistics in this publication, it is recommended that the relevant statistics be rounded. All data are affected by errors in reporting and processing. Registered births and deaths data are also affected by delays in registration. While unrounded figures are provided in tables, accuracy to the last digit is not claimed and should not be assumed. No reliance should be placed on statistics with small values.

ACKNOWLEDGMENTS
71 ABS publications draw extensively on information provided freely by individuals, businesses, governments and other organisations. Their continued cooperation is very much appreciated; without it, the wide range of statistics published by the ABS would not be available. Information received by the ABS is treated in strict confidence as required by the Census and Statistics Act, 1905.

CONFIDENTIALITY
72 The Census and Statistics Act, 1905 provides the authority for the ABS to collect statistical information, and requires that statistical output shall not be published or disseminated in a manner that is likely to enable the identification of a particular person or organisation. This requirement means that the ABS must take care and make assurances that any statistical information about individual respondents cannot be derived from published data.
73 Some techniques used to guard against identification or disclosure of confidential information in statistical tables are suppression of sensitive cells, and random adjustments to cells with very small values.
74 Throughout this publication, different methods of confidentialisation have been used. In some cases cell values have been suppressed and are not available for publication but included in totals where applicable. In these cases data may not sum to totals due to the confidentialisation of individual cells.

ABS PUBLICATIONS
75 ABS publications which may be of interest to users include: